Wireless Communications

Time division multiple access (TDMA) is a classic approach to multiple access in digital cellular wireless communications systems. The authors summarize a number of frequency and time slot allocation techniques for enhancing the capacity and flexibility of TDMA-based systems. They also describe how the problems of fading, delay spread, time variability and interference affect TDMA systems, and how they may he countered and even exploited by appropriate techniques of detection, diversity, coding, adaptive equalization and slow frequency hopping (FH). It is worth emphasizing that the use of one of these techniques, slow random FH, results in a system that is in effect a hybrid of TDMA and code division multiple access (CDMA). >

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Time division multiple access methods for wireless personal communications

An explanation of the widely different technological approaches and technologies being proposed for different interpretations of wireless personal communications services (PCS) is presented. Different wireless communications applications and issues surrounding the applications are discussed. Descriptions of the compromises that have been made in developing specific technologies optimized to serve the cordless telephone and the vehicular mobile radio applications are presented. Characteristics of a technology that is aimed at the widespread pedestrian PCS application and environment are outlined. Different wireless technologies that have been aimed at different applications and environments are compared. >

Wireless network access for personal communications

It is suggested that low-power digital radio as an access technology could be integrated into a local exchange network to provide a ubiquitous personal communications network (PCN). High-quality tetherless communications services that could be provided by such an exchange-network-based PCN are described. A possible low-power exchange access digital radio system for providing these exchange-network based PCS services is discussed. The radio system uses a spectrum-efficient time-division multiple-access (TDMA) architecture made possible by advanced digital signal processing techniques. Control of the frequency reuse system is described, and frequency spectrum needs are indicated. >

A radio system proposal for widespread low-power tetherless communications

The design and performance of linear modulation techniques and RF power amplifiers are discussed Various types of power amplifier are used in the comparison, using simulation, of out-of-band radiation and power efficiency The designs focus on high-frequency silicon bipolar power amplifiers suitable for low-power portable radio applications Two different 4-QAM (4-level quadrature amplitude modulation) schemes are compared Power efficiency as high as 40% can be achieved using a dynamically biased amplifier operating near saturation The effects of nonlinear distortions from power amplifiers on adjacent channel interference as well as bit and block error rate performance are also investigated >

Characterizing the effects of nonlinear amplifiers on linear modulation for digital portable radio communications

The architecture and implementation of a TDMA (time-division multiple access) digital portable communication system using short bursts are considered. The authors describe an efficient and robust TDMA frame structure that requires very low overhead for burst demodulation and synchronization while being robust against both fading and carrier frequency offset. Based on this frame structure, an experimental radio link was implemented, using a hardware architecture that is suitable for digital signal processing and VLSI implementation. Performance results are presented. >

Architecture and implementation of an efficient and robust TDMA frame structure for digital portable communications

The architecture and implementation of a time-division multiple-access digital portable communication system using short bursts are considered. An efficient and robust TDMA frame structure that requires very low overhead for burst demodulation and synchronization while being robust against fading and carrier frequency offset is described. Based on this frame structure, an experimental radio link was implemented by using a hardware architecture that is suitable for digital signal processing and very large-scale integration implementation. Implementation of demodulation, synchronization, error detection, and fading recovery using combined software and off-the-shelf hardware is described, followed by a summary of the performance results. >

H.W. Arnold

Papers

Architecture and implementation of an efficient and robust TDMA frame structure for digital portable communications

Architecture and implementation of an efficient and robust TDMA frame structure for digital portable communications